At present, on the sites with serious dust pollution such as operating mine wells and tunnel construction, filter-type de-dusting devices are commonly used to remove dust in the air through circulating and filtering, so as to purify the air on such working and construction sites and protect the workers' health. The de-dusting device removes dust in the air using filter with very tiny meshes. However, the filter may absorb more and more dust when in use and thus increasing the air circulation resistance, resulting in increasing load of the fan motor, which not only wastes energy but also decrease the de-dusting efficiency, and the fan motor becomes more liable to breakage due to constantly increasing current. All these bring much troubles.